(Random Walk) A stock has the value of 100 on day 0. Each day, the value changes randomly either
one unit upwards with probability 2/3 or two units downwards with probability 1/3. The daily changes are
independent.
a) Compute the probability that, after 50 days, the value > 110.
b) Compute the probability that, after 200 days, the value > 110.
c) Compute the probability that, after 200 days, the value < 90.

I know I should apply central limit theorem to this, but how do I do it?
I've calculated:
Expected value = 0
and
Variance = 2